A particle beam therapy, which is a treatment of a deceased tissue by irradiating it with a particle beam to thereby damage the tissue, is a part of broad-sense radiation therapy. However, unlike a y-ray, an X-ray or like other ray, the imparted dose of a particle beam such as a proton beam, a heavy ion beam, etc., becomes maximum abruptly in a specific depth range (Bragg peak) in a body according to energy of the particle beam. Thus, in the particle beam therapy, it is possible to control the irradiation region (irradiation field), not only as a planar shape, but also in a depth direction by adjusting the energy.
Meanwhile, since the facility of an accelerator that is a beam source for the particle beam therapy is huge, the particle beam emitted from a single beam source is distributed to a plurality of treatment rooms, individually. Although the energy of the particle beam is adjustable by changing the condition of the accelerator, it takes time. Thus, what is generally taken is to provide a device having a transmissive plate of a predetermined thickness, so-called “range shifter”, in each of the treatment rooms, to thereby adjust the energy of the particle beam according to its attenuation amount during transmission in the transmissive plate (see, for example, Patent Documents 1 to 9).